Electrode assembly with improved stability and method of manufacturing the same

ABSTRACT

An electrode assembly includes a cell stack part having (a) a structure in which one kind of radical unit is repeatedly disposed, or (b) a structure in which at least two kinds of radical units are disposed in a predetermined order. The one kind of radical unit has a four-layered structure in which first electrode, first separator, second electrode and second separator are sequentially stacked or a repeating structure in which the four-layered structure is repeatedly stacked. Each of the at least two kinds of radical units are stacked by ones to form the four-layered structure or the repeating structure. The separator has a larger size than the electrode to expose an edge part of the separator to outside of the electrode and the separator. The edge parts of the separators included in one radical unit or in the cell stack part are attached to form a sealing part.

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application is a Continuation of U.S. applicationSer. No. 14/468,786, filed Aug. 26, 2014, which is a Continuation ofInternational Application No. PCT/KR2014/001268 filed on Feb. 17, 2014,which claims priority to Patent Application Nos. 10-2013-0016512 filedin the Republic of Korea on Feb. 15, 2013 and 10-2014-0017701 filed inthe Republic of Korea on Feb. 17, 2014. The entire contents of all ofthe above applications are hereby incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an electrode assembly with improvedstability and a method of manufacturing the same, and more particularly,to an electrode assembly with improved stability capable of decreasingshrinkage ratio of a separator and a method of manufacturing the same.

Description of the Related Art

Secondary batteries receive attention as a power source of an electricvehicle (EV), a hybrid electric vehicle (HEV), a parallel hybridelectric vehicle (PHEV), etc., suggested as a means for solving the airpollution of a common gasoline vehicle, a diesel vehicle, etc. usingfossil fuel. In a medium and large size device such as a vehicle, highpower and high capacity are necessary, and a medium and large sizebattery module in which a plurality of battery cells are electricallyconnected is used.

However, since the medium and large size battery module is preferablymanufactured to have a small size and light weight, a prismatic typebattery, a pouch type battery, etc. having high stacking degree andlight weight with respect to capacity have been mainly manufactured asthe battery cell of the medium and large size battery module.

In general, an electrode assembly is classified according to thestructure of the electrode assembly having a cathode/separator/anodestructure, and typically is classified into a jelly-roll type (rolltype) electrode assembly having a rolled structure of long sheet typecathodes and anodes with a long sheet type separator disposedtherebetween, and a stack-type (laminated type) electrode assemblyobtained by stacking a plurality of cathodes and anodes cut into acertain size with a separator therebetween in sequence. Preferably, thestructure of the electrode assembly includes a stack-type structure anda stack/folding type structure.

The stack type structure is widely known in the art, and the explanationthereon will be omitted in the present disclosure. Detailed descriptionof an electrode assembly having the stack/folding type structure isdisclosed in Korean Patent Application Publication Nos. 2001-0082058,2001-0082059 and 2001-0082060 filed by the present Applicant.

Referring to FIG. 1, in an electrode assembly of a stack/folding typestructure 1, a plurality of radical units 1 a, 1 b, 2, 3 and 4,including a cathode, a separator and an anode stacked in sequence areoverlapped, and in each of overlapped parts, a separator sheet 5 isinterposed. The separator sheet 5 has a length for wrapping the radicalunits and is disposed at the overlapped parts of the radical units whilewrapping each of the radical units from the radical unit 1 a to theoutermost radical unit 4 continuously.

The terminal part of the separator sheet 5 is finished by heat welding,by attaching using an adhesive tape 6, or the like. The stack/foldingtype electrode assembly is manufactured by arranging the radical units 1a, 1 b, 2, 3 and 4 on the separator sheet 5 having a long length androlling the separator sheet 5 from one terminal part thereof one by one.However, in this structure, temperature gradient may be generatedbetween the radical units 1 a, 1 b and 2 positioned in the centerportion and the radical units 3 and 4 positioned at the outer portion,thereby generating different heat emitting efficiencies. Thus, lifetimemay decrease after use for a long time.

In general, a separator provided in a radical unit is mainly formed byusing a polymer material, and has shrinking properties by heat. Anovercharge test and a hot box test are performed with respect to anelectrode assembly or a secondary battery including the same to evaluatestability. During performing the tests, some bad electrode assemblies orsecondary batteries including the same may ignite. The ignition may begenerated because of the shrinkage of the separator due to heat and theshort generated through the contact of a cathode and an anode.

Meanwhile, even in a commercial secondary battery after performing thetest for stability evaluation, a risk of the shrinkage of a separatordue to heat applied from the outside during use or heat generated in thesecondary battery, and the generation of short as described above ispresent.

To prevent the above defects, a separator having a larger size than anelectrode may be applied in an electrode assembly.

However, in the electrode assembly of a stack/folding type structure 1,the edge parts of a separator are not attached to an electrode, and aseries of manufacturing processes of a secondary battery is conductedwithout conducting specific treatment with respect to the edge parts ofthe separator. Thus, there is a high risk of generating short due toovercharge, overheat, etc. In addition, since specific treatment withrespect to the edge parts of the separator is not conducted in anelectrode assembly of a stack type structure, there also is a high riskof generating short as in the electrode assembly of a stack/folding typestructure 1.

Thus, both in the electrode assembly of a stack/folding type structure 1and the electrode assembly of the stack type, the separator is necessaryto have a quite large size when compared to the electrodes to definitelyprevent the generation of short between the cathode and the anode. Inthis case, the volume of the secondary battery may increase.

Here, since the separator is more than necessary, the production cost ofa secondary battery may increase.

SUMMARY OF THE INVENTION

An aspect of the present disclosure for solving the above-describeddefects provides an electrode assembly having decreased risk of innershort and improved stability even though using a separator having thesame as or a somewhat smaller size of that of a common separator, and amethod of manufacturing the same.

Another aspect of the present invention is to provide an electrodeassembly having decreased unit production cost and having improvedstability, and a manufacturing method thereof.

A further aspect of the present invention is to provide an electrodeassembly with improved stability and a manufacturing method thereof bywhich the electrode assembly may be manufactured only using one kind ofbi-cells.

According to an aspect of the present disclosure, there is provided anelectrode assembly with improved stability including a cell stack parthaving (a) a structure in which one kind of radical unit is repeatedlydisposed, the one kind of radical unit having a same number ofelectrodes and separators which are alternately disposed and integrallycombined, or (b) a structure in which at least two kinds of radicalunits are disposed in a predetermined order, the two kinds of radicalunits having a same number of electrodes and separators which arealternately disposed and integrally combined. The one kind of radicalunit of (a) has a four-layered structure in which a first electrode, afirst separator, a second electrode and a second separator aresequentially stacked together or a repeating structure in which thefour-layered structure is repeatedly stacked, and each of the at leasttwo kinds of radical units of (b) are stacked by ones in thepredetermined order to form the four-layered structure or the repeatingstructure in which the four-layered structure is repeatedly stacked. Theseparator has a larger size than the electrode to expose an edge part ofthe separator to the outside of the electrode and the separator. Theedge parts of the separators included in one radical unit are attachedto each other to form a sealing part, or the edge parts of theseparators included in the cell stack part are attached to each other toform the sealing part.

According to another aspect of the present disclosure, there is provideda method of manufacturing an electrode assembly with improved stabilityincluding a step of forming one kind of a radical unit having analternately stacked structure of a same number of electrodes andseparators, or at least two kinds of radical units having an alternatelystacked structure of a same number of electrodes and separators (S10); astep of forming a sealing part by facing edge parts of the separatorsincluded in one radical unit and applying heat and pressure (S20); and astep of forming a cell stack part by repeatedly stacking the one kind ofthe radical units after performing steps S10 and S20, or by stacking theat least two kinds of the radical units after performing steps S10 andS20 in a predetermined order (S22). The one kind of radical unit has afour-layered structure in which a first electrode, a first separator, asecond electrode and a second separator are sequentially stackedtogether or a repeating structure in which the four-layered structure isrepeatedly stacked, and each of the at least two kinds of radical unitsare stacked by ones in the predetermined order to form the four-layeredstructure or the repeating structure in which the four-layered structureis repeatedly stacked.

According to further another aspect of the present disclosure, there isprovided a method of manufacturing an electrode assembly with improvedstability including a step of forming one kind of a radical unit havingan alternately stacked structure of a same number of electrodes andseparators, or at least two kinds of radical units having an alternatelystacked structure of a same number of electrodes and separators (S10); astep of forming a cell stack part by repeatedly stacking the one kind ofthe radical units, or by stacking the at least two kinds of the radicalunits in a predetermined order (S14); and a step of forming a sealingpart by facing edge parts of the separators included in the cell stackpart and applying heat and pressure (S30). The one kind of radical unithas a four-layered structure in which a first electrode, a firstseparator, a second electrode and a second separator are sequentiallystacked together or a repeating structure in which the four-layeredstructure is repeatedly stacked, and each of the at least two kinds ofradical units are stacked by ones in the predetermined order to form thefour-layered structure or the repeating structure in which thefour-layered structure is repeatedly stacked.

According to the present invention, the following effects may beobtained.

First, an electrode assembly having decreased risk of inner short andimproved stability even though using a separator having the same as or asomewhat smaller size of that of a common separator, and a method ofmanufacturing the same, may be provided.

Second, an electrode assembly having decreased production cost andhaving improved stability and a method of manufacturing the same, may beprovided.

Third, an electrode assembly having improved stability and a method ofmanufacturing the same by which the electrode assembly may bemanufactured only using one kind of bi-cells, may be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a cross-sectional view conceptually illustrating a foldingtype structure of a common electrode assembly;

FIG. 2 is a side view illustrating a first structure of a radical unitaccording to the present disclosure;

FIG. 3 is a side view illustrating a second structure of a radical unitaccording to the present disclosure;

FIG. 4 is a side view illustrating a cell stack part formed by stackingthe radical units of FIG. 2;

FIG. 5 is a side view illustrating a third structure of a radical unitaccording to the present disclosure;

FIG. 6 is a side view illustrating a fourth structure of a radical unitaccording to the present disclosure;

FIG. 7 is a side view illustrating a cell stack part formed by stackingthe radical units of FIG. 5 and the radical units of FIG. 6;

FIG. 8 is a process diagram illustrating a manufacturing process of aradical unit according to the present disclosure;

FIG. 9 is a perspective view illustrating a cell stack part formed bystacking radical units having different sizes;

FIG. 10 is a side view illustrating the cell stack part of FIG. 9;

FIG. 11 is a perspective view illustrating a cell stack part formed bystacking radical units having different geometric shapes;

FIG. 12 is a side view illustrating a first structure of a cell stackpart including a radical unit and a first auxiliary unit according tothe present disclosure;

FIG. 13 is a side view illustrating a second structure of a cell stackpart including a radical unit and a first auxiliary unit according tothe present disclosure;

FIG. 14 is a side view illustrating a third structure of a cell stackpart including a radical unit and a second auxiliary unit according tothe present disclosure;

FIG. 15 is a side view illustrating a fourth structure of a cell stackpart including a radical unit and a second auxiliary unit according tothe present disclosure;

FIG. 16 is a side view illustrating a fifth structure of a cell stackpart including a radical unit and a first auxiliary unit according tothe present disclosure;

FIG. 17 is a side view illustrating a sixth structure of a cell stackpart including a radical unit and a first auxiliary unit according tothe present disclosure;

FIG. 18 is a side view illustrating a seventh structure of a cell stackpart including a radical unit and a second auxiliary unit according tothe present disclosure;

FIG. 19 is a side view illustrating an eighth structure of a cell stackpart including a radical unit and a second auxiliary unit according tothe present disclosure;

FIG. 20 is a side view illustrating a ninth structure of a cell stackpart including a radical unit and a first auxiliary unit according tothe present disclosure;

FIG. 21 is a side view illustrating a tenth structure of a cell stackpart including a radical unit, a first auxiliary unit, and a secondauxiliary unit according to the present disclosure;

FIG. 22 is a side view illustrating an eleventh structure of a cellstack part including a radical unit and a second auxiliary unitaccording to the present disclosure;

FIG. 23 is a cross-sectional view illustrating a stacked state of aseparator on the first structure of the radical unit in FIG. 2;

FIG. 24 is a cross-sectional view illustrating a stacked state of aseparator on an uppermost electrode after stacking the first structureof the radical unit in FIG. 2 twice;

FIG. 25 is a cross-sectional view illustrating a cell stack partincluding a sealing part by attaching edge parts of the separators inFIG. 23; and

FIG. 26 is a cross-sectional view illustrating a cell stack partincluding a sealing part by attaching edge parts of the separators inFIG. 23.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Exemplary embodiments of an electrode assembly with improved stabilityand a method of manufacturing the same according to the presentdisclosure will now be described in detail with reference to theaccompanying drawings.

It will be understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the inventive concept to those skilled in the art.Although the preferred embodiments of the present disclosure have beendisclosed for illustrative purpose, those skilled in the art willappreciate that various modifications, additions and substitutions canbe made without departing from the scope and spirit of the inventiveconcept as defined in the accompanying claims.

In the drawings, the sizes and relative sizes of each elements or aspecific part composing the elements may be exaggerated or brieflyillustrated for effective explanation and clearance of technicalcontents. Thus a real size is not reflected to the size of each element.Particular explanation on relevant known functions or constituents isconsidered to unnecessarily confuse the gist of the present disclosure,the explanation will be omitted.

An electrode assembly according to the present disclosure includes acell stack part having a structure obtained by stacking radical unitsrepeatedly or in a predetermined order, or having a structure obtainedby further stacking an auxiliary unit on the cell stack part. Inaddition, a sealing part may be formed by attaching the edge parts ofseparators having a larger size than electrodes by the radical unit, ora sealing part may be formed by attaching the edge parts of allseparators present in the cell stack part having a structure obtained bystacking radical units repeatedly or in a predetermined order at thesame time.

The structure of the radical unit and the auxiliary unit possiblystacked on the radical unit, and the structure of the cell stack parthaving a plurality of stacked radical units may be attained diversely.Therefore, these structures will be explained first, and the formationof the sealing part in the radical unit or the formation of the sealingpart in the cell stack part at the same time will be subsequentlyexplained.

Cell Stack Part

The cell stack part has a structure obtained by repeatedly disposing onekind of radical units or a structure obtained by disposing at least twokinds of radical units in a predetermined order, for example,alternately. This will be described below in more detail.

[Structure of Radical Unit]

In an electrode assembly according to the present disclosure, a radicalunit is formed by alternately disposing electrodes and separators. Here,the same number of electrodes and separators are disposed. For example,as illustrated in FIG. 2 a radical unit 110 a may be formed by stackingtwo electrodes 111 and 113 and two separators 112 and 114. Here, acathode and an anode may naturally face each other through theseparator. When the radical unit is formed as described above, anelectrode 111 is positioned at one end part of the radical unit (seeelectrode 111 in FIGS. 2 and 2) and a separator 114 is positioned at theother end part of the radical unit (see separator 114 in FIGS. 2 and 2).

The electrode assembly according to the present disclosure is basicallycharacterized in that the cell stack part or electrode assembly isformed by only stacking the radical units. That is, the presentdisclosure has a basic characteristic in that the cell stack part isformed by repeatedly stacking one kind of radical unit or by stacking atleast two kinds of radical units in a predetermined order. To realizethe above-described characteristic, the radical unit may have thefollowing structure.

First, the radical unit may be formed by stacking a first electrode, afirst separator, a second electrode, and a second separator in sequence.In more detail, a first electrode 111, a first separator 112, a secondelectrode 113, and a second separator 114 may be stacked in sequencefrom an upper side to a lower side, as illustrated in FIG. 2, or fromthe lower side to the upper side, as illustrated in FIG. 3, to formradical units 110 a and 110 b. The radical unit having theabove-described structure may be referred to as a first radical unit.Here, the first electrode 111 and the second electrode 113 may beopposite types of electrodes. For example, when the first electrode 111is a cathode, the second electrode 113 may be an anode.

As described above, when the radical unit is formed by stacking thefirst electrode 111, the first separator 112, the second electrode 113,and the second separator 114 in sequence, a cell stack part 100 a may beformed by only repeatedly stacking the one kind of radical units 110 a,as illustrated in FIG. 4. Here, the radical unit may have aneight-layered structure or twelve-layered structure in addition to afour-layered structure. That is, the radical unit may have a repeatingstructure in which the four-layered structure is repeatedly disposed.For example, the radical unit may be formed by stacking the firstelectrode 111, the first separator 112, the second electrode 113, thesecond separator 114, the first electrode 111, the first separator 112,the second electrode 113, and the second separator 114 in sequence.

Alternatively, the radical unit may be formed by stacking the firstelectrode 111, the first separator 112, the second electrode 113, thesecond separator 114, the first electrode 111, and the first separator112 in sequence, or by stacking the second electrode 113, the secondseparator 114, the first electrode 111, the first separator 112, thesecond electrode 113, and the second separator 114 in sequence. Theradical unit having the former structure may be referred to as a secondradical unit and the radical unit having the latter structure may bereferred to as a third radical unit.

In more detail, the second radical unit 100 c may be formed by stackingthe first electrode 111, the first separator 112, the second electrode113, the second separator 114, the first electrode 111, and the firstseparator 112 in sequence from the upper side to the lower side, asillustrated in FIG. 5. Also, the third radical structure 110 d may beformed by stacking the second electrode 113, the second separator 114,the first electrode 111, the first separator 112, the second electrode113, and the second separator 114 in sequence from the upper side to thelower side, as illustrated in FIG. 6. As noted above, the stacking maybe conducted in sequence from the lower side to the upper side.

When only one of the second radical units 110 c and one of the thirdradical units 110 d are stacked, a repeating structure in which thefour-layered structure is repeatedly stacked may be formed. Thus, whenthe second radical unit 110 c and the third radical unit 110 d arealternately stacked one by one, the cell stack part 100 b may be formedby stacking only the second and third radical units, as illustrated inFIG. 7. For reference, when three kinds of radical units are prepared,the cell stack part may be formed by stacking the radical units in apredetermined order, for example, the first radical unit, the secondradical unit, the third radical unit, the first radical unit again, thesecond radical unit, and the third radical unit.

As described above, the one kind of radical unit in the presentdisclosure has a four-layered structure in which a first electrode, afirst separator, a second electrode and a second separator aresequentially stacked, or has a repeating structure in which thefour-layered structure is repeatedly stacked. Also, at least two kindsof radical units in the present disclosure are stacked only by ones in apredetermined order to form the four-layered structure or the repeatingstructure in which the four-layered structure is repeatedly disposed.For example, the first radical unit forms a four-layered structure byitself, and the second radical unit and the third radical unit form atwelve-layered structure by stacking one of each, that is, two radicalunits in total.

Thus, the cell stack part or electrode assembly may be formed only bystacking, that is, by repeatedly stacking one kind of radical unit or bystacking at least two kinds of radical units in a predetermined order.

The cell stack part of the present disclosure may be formed by stackingthe radical units one by one. That is, the cell stack part may bemanufactured by forming the radical units and then stacking the radicalunits repeatedly or in a predetermined order. As described above, thecell stack part of the present disclosure may be formed by only stackingthe radical units. Therefore, the radical units of the presentdisclosure may be very accurately aligned. When the radical unit isaccurately aligned, the electrode and the separator may also beaccurately aligned in the cell stack part. In addition, the cell stackpart or electrode assembly may be improved in productivity. This is donebecause the manufacturing process is very simple.

[Manufacture of Radical Unit]

A manufacturing process of the first radical unit will be exemplarilydescribed with reference to FIG. 8. First, a first electrode material121, a first separator material 122, a second electrode material 123 anda second separator material 124 are prepared. Here, the first separatormaterial 122 and the second separator material 124 may be the same. Thefirst electrode material 121 is cut into a certain size through a cutterC1, and the second electrode material 123 is cut into a certain sizethrough a cutter C2. Then, the first electrode material 121 is stackedon the first separator material 122, and the second electrode material123 is stacked on the second separator material 124.

Then, it is preferable that the electrode materials and the separatormaterials are attached to each other through laminators L1 and L2.Through the attachment, a radical unit in which the electrodes and theseparators are integrally combined may be formed. The combining methodmay be diverse. The laminators L1 and L2 may apply pressure to thematerials or apply pressure and heat to the materials to attach thematerials to each other. Because of the attachment, the stacking of theradical units may be more easily performed while manufacturing the cellstack part. Also, the alignment of the radical units may be also easilyaccomplished because of the attachment. After the attachment, the firstseparator material 122 and the second separator material 124 are cutinto a certain size through a cutter C3 to manufacture the radical unit110 a.

As described above, the electrode may be attached to the adjacentseparator in the radical unit. Alternatively, the separator may beattached to the adjacent electrode. Here, it is preferable that anentire surface of the electrode facing the adjacent separator isattached to the adjacent separator. In this case, the electrode may bestably fixed to the separator. Typically, the electrode has a size lessthan that of the separator.

For this, an adhesive may be applied to the separator. However, when theadhesive is used, it is necessary to apply the adhesive over an adhesionsurface of the separator in a mesh or dot shape. This is because if theadhesive is closely applied to the entire adhesion surface, reactiveions such as lithium ions may not pass through the separator. Thus, whenthe adhesive is used, it is difficult to allow the overall surface ofthe electrode to closely attach to the adjacent separator.

Alternatively, use of the separator including the coating layer havingadhesive strength makes it possible to generally attach the electrode tothe separator. This will be described below in more detail. Theseparator may include a porous separator base material such as apolyolefin-based separator base material and a porous coating layer thatis generally applied to one side or both sides of the separator basematerial. Here, the coating layer may be formed of a mixture ofinorganic particles and a binder polymer that binds and fixes theinorganic particles to each other.

Here, the inorganic particles may improve thermal stability of theseparator. That is, the inorganic particles may prevent the separatorfrom being contracted at a high temperature. In addition, the binderpolymer may fix the inorganic particles to improve mechanical stabilityof the separator. Also, the binder polymer may attach the electrode tothe separator. Since the binder polymer is generally distributed in thecoating layer, the electrode may closely adhere to the entire adhesionsurface of the separator, unlike the foregoing adhesive. Thus, when theseparator is used as described above, the electrode may be more stablyfixed to the separator. To enhance the adhesion, the above-describedlaminators may be used.

The inorganic particles may have a densely packed structure to forminterstitial volumes between the inorganic particles over the overallcoating layer. Here, a pore structure may be formed in the coating layerby the interstitial volumes that are defined by the inorganic particles.Due to the pore structure, even though the coating layer is formed onthe separator, the lithium ions may smoothly pass through the separator.For reference, the interstitial volume defined by the inorganicparticles may be blocked by the binder polymer according to a positionthereof.

Here, the densely packed structure may be explained as a structure inwhich gravels are contained in a glass bottle. Thus, when the inorganicparticles form the densely packed structure, the interstitial volumesbetween the inorganic particles are not locally formed in the coatinglayer, but generally formed in the coating layer. As a result, when eachof the inorganic particles increases in size, the pore formed by theinterstitial volume also increases in size. Due the above-describeddensely packed structure, the lithium ions may smoothly pass through theseparator over the entire surface of the separator.

The radical units may also adhere to each other in the cell stack part.For example, if the adhesive or the above-described coating layer isapplied to a bottom surface of the second separator 114 in FIG. 2, theother radical unit may adhere to the bottom surface of the secondseparator 114.

Here, the adhesive strength between the electrode and the separator inthe radical unit may be greater than that between the radical units inthe cell stack part. It is understood, that the adhesive strengthbetween the radical units may not be provided. In this case, when theelectrode assembly or the cell stack part is disassembled, the electrodeassembly may be separated into the radical units due to a difference inthe adhesive strength. For reference, the adhesive strength may beexpressed as delamination strength. For example, the adhesive strengthbetween the electrode and the separator may be expressed as a forcerequired for separating the electrode from the separator. In thismanner, the radical unit may not be bonded to the adjacent radical unitin the cell stack part, or may be bonded to the adjacent radical unit inthe cell stack part by means of a bonding strength differing from abonding strength between the electrode and the separator.

For reference, when the separator includes the above-described coatinglayer, it is not preferable to perform ultrasonic welding on theseparator. Typically, the separator has a size greater than that of theelectrode. Thus, there may be an attempt to bond the edge of the firstseparator 112 to the edge of the second separator 114 through theultrasonic welding. Here, it is necessary to directly press an object tobe welded through a horn in the ultrasonic welding. However, when theedge of the separator is directly pressed through the horn, theseparator may adhere to the horn due to the coating layer having theadhesive strength. As a result, the welding apparatus may be brokendown.

[Modification of Radical Unit]

Until now, the radical units having the same size have been explained.However, the radical units may have different sizes. When stacking theradical units having different sizes, cell stack parts having variousshapes may be manufactured. Herein, the size of the radical unit isexplained with reference to the size of the separator, because,typically, the separator is larger than the electrode.

Referring to FIGS. 9 and 10, a plurality of radical units is preparedand may be classified into at least two groups having different sizes(see reference numerals 1101 a, 1102 a and 1103 a in FIG. 10). Bystacking the radical units according to their sizes, a cell stack part100 c having a structure of a plurality of steps may be formed. FIGS. 9and 10 illustrate an embodiment in which the cell stack part includesthree steps obtained by stacking the radical units 1101 a, 1102 a and1103 a classified into three groups, in which the radical units havingthe same size are stacked together, is illustrated. For reference, theradical units included in one group may form two or more steps.

When the plurality of steps is formed as described above, it ispreferable that the radical unit has a structure of the first radicalunit, that is, the above-described four-layered structure or therepeating structure in which the four-layered structure is repeatedlystacked. (Herein, the radical units are considered to be included in onekind of radical unit even though the radical units have the same stackedstructures but have different sizes.)

Preferably, the same number of cathodes and the anodes are stacked inone step. Also, it is preferable that opposite electrodes face eachother through a separator between one step and another step. Forexample, in case of the second and third radical units, two kinds of theradical units are necessary for forming one step.

However, in case of the first radical unit, only one kind of radicalunit is necessary for forming one step as illustrated in FIG. 10. Thus,when the radical unit has the four-layered structure or the repeatingstructure in which the four-layered structure is repeatedly stacked,number of kinds of radical units may decrease even though a plurality ofthe steps is formed.

Also, in case of the second and the third radical units, at least one ofthe two kinds of the radical units are necessary to be stacked to formone step. Thus, the one step may have at least a twelve-layeredstructure. However, in case of the first radical unit, only one kind ofradical unit is necessary to be stacked to form one step. Thus, one stepmay have at least a four-layered structure. As a result, when theradical unit has the four-layered structure or the repeating structurein which the four-layered structure is repeatedly stacked, the thicknessof each step may be easily controlled when forming a plurality of steps.

The radical units may have not only different sizes but also differentgeometric shapes. For example, the radical units may have differentsizes and different edge shapes, and may or may not have a through holeas illustrated in FIG. 11. More particularly, as illustrated in FIG. 11,a plurality of radical units classified into three groups may form threesteps by stacking the radical units having the same geometric shapes.For this, the radical units may be classified into at least two groups(each of the groups has different geometric shape). Similarly, theradical unit may preferably have the four-layered structure or therepeating structure in which the four-layered structures are repeatedlystacked, that is, the structure of the first radical unit. (Herein, theradical units are considered to be included in one kind of radical uniteven though the radical units have the same stacked structure but havedifferent geometric shapes.)

[Auxiliary Unit]

The cell stack part may further include at least one among a firstauxiliary unit and a second auxiliary unit. First, the first auxiliaryunit will be described below. In the present disclosure, an electrode ispositioned at one end of the radical unit, and a separator is positionedat the other end of the radical unit. When the radical units are stackedin sequence, the electrode may be positioned at the uppermost portion orat the lowermost portion of the cell stack part (see reference numeral116 in FIG. 12, and this electrode may be referred to as a terminalelectrode 116). The first auxiliary unit is additionally stacked on theterminal electrode.

In more detail, when the terminal electrode 116 is a cathode, the firstauxiliary unit 130 a may be formed by stacking outward from the terminalelectrode 116, a separator 114, an anode 113, a separator 112, and acathode 111 in sequence, as illustrated in FIG. 12. On the other hand,when the terminal electrode 116 is an anode, the first auxiliary unit130 b may be formed by stacking outward from the terminal electrode 116,the separator 114, and the cathode 113 in sequence, as illustrated inFIG. 13.

In the cell stack parts 100 d and 100 e, a cathode may be positioned atthe outermost portion of a terminal electrode through the firstauxiliary units 130 a and 130 b, as illustrated in FIGS. 12 and 13. Inthis case, in the cathode positioned at the outermost portion, that is,the cathode of the first auxiliary unit, an active material layer ispreferably coated on only one side facing the radical unit (one sidefacing downward in FIG. 12) among both sides of the current collector.When the one side of the current collector is coated with the activematerial layer as described above, the active material layer is notpositioned at the outermost portion of the cell stack part. Thus, wasteof the active material layer may be prevented. For reference, since thecathode emits, for example, lithium ions, when the cathode is positionedat the outermost portion, the capacity of a battery may be improved.

Next, a second auxiliary unit will be described below. The secondauxiliary unit performs the same function as the first auxiliary unit,which will be described below in more detail. In the present disclosure,an electrode is positioned at one end of the radical unit, and aseparator is positioned at the other end of the radical unit. When theradical units are stacked in sequence, the separator may be positionedat the uppermost portion or at the lowermost portion of the cell stackpart (see reference numeral 117 in FIG. 14, and this separator may bereferred to as a terminal separator 117). The second auxiliary unit isadditionally stacked on the terminal separator.

In more detail, when the electrode 113 contacting the terminal separator117 is a cathode in the radical unit, the second auxiliary unit 140 amay be formed by stacking from the terminal separator 117, an anode 111,a separator 112, and a cathode 113 in sequence, as illustrated in FIG.14. On the other hand, when the electrode 113 contacting the terminalseparator 117 is an anode in the radical unit, the second auxiliary unit140 b may be formed as the cathode 111, as illustrated in FIG. 15.

In the cell stack parts 100 f and 100 g, a cathode may be positioned atthe outermost portion of a terminal separator through the secondauxiliary units 140 a and 140 b, as illustrated in FIGS. 14 and 15. Inthis case, in the cathode positioned at the outermost portion, that is,the cathode of the second auxiliary unit, an active material layer ispreferably coated on only one side facing the radical unit (one sidefacing upward in FIG. 14) among both sides of the current collector, assimilar to the cathode of the first auxiliary unit.

The first auxiliary unit and the second auxiliary unit may havedifferent structures from those described above. First, the firstauxiliary unit will be described below. When the terminal electrode 116is a cathode as illustrated in FIG. 16, the first auxiliary unit 130 cmay be formed by stacking from the terminal electrode 116, a separator114, and an anode 113 in sequence. On the other hand, when the terminalelectrode 116 is an anode as illustrated in FIG. 17, the first auxiliaryunit 130 d may be formed by stacking from the terminal electrode 116, aseparator 114, a cathode 113, a separator 112, and an anode 111 insequence.

In the cell stack parts 100 h and 100 i, an anode may be positioned atthe outermost portion of the terminal electrode through the firstauxiliary units 130 c and 130 d, as illustrated in FIGS. 16 and 17.

Next, the second auxiliary unit will be described below. As illustratedin FIG. 18, when the electrode 113 contacting the terminal separator 117is a cathode in the radical unit, the second auxiliary unit 140 c may beformed as an anode 111. As illustrated in FIG. 19, when the electrode113 contacting the terminal separator 117 is an anode in the radicalunit, the second auxiliary unit 140 d may be formed by stacking from theterminal separator 117, the cathode 111, the separator 112, and theanode 113 in sequence. In the cell stack parts 100 j and 100 k, an anodemay be positioned at the outermost portion of the terminal separatorthrough the second auxiliary units 140 c and 140 d, as illustrated inFIGS. 18 and 19.

For reference, an anode may make a reaction with an aluminum layer of abattery case (for example, a pouch-type case) due to potentialdifference. Thus, the anode is preferably insulated from the batterycase by means of a separator. For this, the first and second auxiliaryunits in FIGS. 16 to 19 may further include a separator at the outerportion of the anode. For example, the first auxiliary unit 130 e inFIG. 20 may further include a separator 112 at the outermost portionthereof when compared to the first auxiliary unit 130 c in FIG. 16. Forreference, when the auxiliary unit includes the separator, the alignmentof the auxiliary units in the radical unit may be easily performed.

A cell stack part 100 m may be formed as illustrated in FIG. 21. Aradical unit 110 b may be formed by stacking from the lower portion tothe upper portion, a first electrode 111, a first separator 112, asecond electrode 113, and a second separator 114 in sequence. In thiscase, the first electrode 111 may be a cathode, and the second electrode113 may be an anode.

A first auxiliary unit 130 f may be formed by stacking from the terminalelectrode 116, the separator 114, the anode 113, the separator 112 andthe cathode 111 in sequence. In this case, in the cathode 111 of thefirst auxiliary unit 130 f, only one side of a current collector facingthe radical unit 110 b among both sides of the current collector may becoated with an active material layer.

Also, a second auxiliary unit 140 e may be formed by stacking from theterminal separator 117, the cathode 111 (the first cathode), theseparator 112, the anode 113, the separator 114, and the cathode 118(the second cathode) in sequence. In this case, in the cathode 118 (thesecond cathode) of the second auxiliary unit 140 e positioned at theoutermost portion, only one side of a current collector facing theradical unit 110 b among both sides of the current collector may becoated with an active material layer.

Finally, a cell stack part 100 n may be formed as illustrated in FIG.22. A radical unit 110 e may be formed by stacking from the upperportion to the lower portion, a first electrode 111, a first separator112, a second electrode 113, and a second separator 114 in sequence. Inthis case, the first electrode 111 may be an anode, and the secondelectrode 113 may be a cathode. Also, a second auxiliary unit 140 f maybe formed by stacking from the terminal separator 117, the anode 111,the separator 112, the cathode 113, the separator 114, and the anode 119in sequence.

Until now, the structure of the radical unit, the structure of theauxiliary unit that may be stacked on the radical unit, and thestructure of the cell stack part having the plurality of stacked radicalunits have been explained. Hereinafter, the manufacturing of the cellstack part (electrode assembly) by forming a sealing part A at theradical unit itself or by forming a sealing part A at the cell stackpart at the same time will be explained referring to the first radicalunit illustrated in FIG. 2 for convenience.

The electrode assembly may correspond to the cell stack part itself orthe cell stack part wrapped in a tape for fixing. Thus, the electrodeassembly according to the present disclosure is provided with a cellstack part having a repeatedly stacked structure of one kind of theradical units including the same number of alternately stackedelectrodes and separators, or having a stacked structure of two or morekinds of the radical units including the same number of alternatelystacked electrodes and separators in a predetermined order.

FIG. 23 is a cross-sectional view illustrating a stacked state of aseparator on a first structure of the radical unit in FIG. 2, and FIG.24 is a cross-sectional view illustrating a stacked state of a separatoron an uppermost electrode after stacking a first structure of theradical unit in FIG. 2 twice.

As shown in FIGS. 23 and 24, a separator S is additionally stacked onthe uppermost electrode of the cell stack part, and the top surface ofthe uppermost electrode and the bottom surface of the lowermostelectrode are covered with separators. When the cell stack parts shownin FIGS. 23 and 24 are turned up and down, the separators S may beadditionally stacked on the lowermost electrodes of the cell stackparts.

The edge portions of adjacent separators in FIGS. 23 and 24 are placedto meet each other, and heat and pressure are applied to attach the edgeparts of the separators, thereby forming sealing parts A illustrated inFIGS. 25 and 26.

Meanwhile, the sealing part A may be formed by attaching the edge partsof the separators included in one radical unit during manufacturing theelectrode assembly. Alternatively, the sealing part A may be formed bystacking the radical units (of course, the auxiliary unit may be stackedtogether) to form the cell stack part and then, attaching the edge partsof all of the separators included in the cell stack parts together.

Hereinafter, an embodiment of the manufacturing method of the electrodeassembly according to the present invention will be described in moredetail.

First, a step of manufacturing one kind of radical units having analternately stacked structure of the same number of electrodes andseparators or two, or more kinds of radical units having an alternatelystacked structure of the same number of electrodes and separators isconducted (S10).

Then, a step of placing the edge parts of the separators included in oneradical unit to meet each other, and forming a sealing part A byapplying heat and pressure is conducted (S20).

After that, a step of manufacturing a cell stack part is conducted byrepeatedly stacking one kind of the radical units after performing StepS10 and Step S20, or by stacking two or more kinds of the radical unitsafter performing Step S10 and Step S20 in order (S22).

As described above, after forming the sealing part A of the edge partsof the separators in each of the radical units by performing Steps S10,S20 and S22 in sequence, a cell stack part (an electrode assembly)having a stacked structure of the radical units may be manufactured.

In another embodiment of the manufacturing method of the electrodeassembly according to the present disclosure, Step S10 is performedfirst as in the above embodiment, and a step of manufacturing a cellstack part by repeatedly stacking one kind of the radical units or bystacking two or more kinds of the radical units in order is performed(S14). Then, the edge parts of separators included in the cell stackpart are placed to meet each other, and heat and pressure are applied toform a sealing part A (S30).

Through conducting Steps S10, S14 and S30 in sequence, a cell stack partis manufactured first by stacking the radical units without forming thesealing part A from the edge parts of the separators provided in theradical units, and then, the sealing part A is formed by using the edgeparts of all the separators included in the cell stack part at the sametime.

When the cell stack part shown in FIG. 4 is assumed to be manufacturedby stacking the first radical units, and an additional separator S isstacked on the uppermost electrode of the first radical unit positionedat the uppermost portion of the cell stack part in FIG. 4, a cell stackpart including the separators at both of the uppermost and the lowermostparts may be manufactured.

Meanwhile, the heat and the pressure applied to the edge parts ofadjacent separators to form the sealing part A in Step S20 and Step S30,are preferably and respectively 50° C. to 100° C. and 10 gf/cm² to 20gf/cm². In addition, the formation of a satisfactory sealing part A maybe performed by only applying the heat and the pressure to the edgeparts of the adjacent separators for 3 to 5 seconds in Step S20 or StepS30.

Accordingly, the time necessary for the manufacture of electrodeassembly may not significantly increase due to the forming steps (S20and S30) of the sealing part A.

A pressure of about 100 Kgf/cm² is necessary to attach the cathode andthe anode, on the contrary, the above described pressure of 10 gf/cm² to20 gf/cm² applied to the edge parts of the separators for the formationof the sealing part A is sufficient. Thus, the sealing part A may beformed by applying significantly less pressure than that applied toattach the cathode and the anode to the separator.

Hereinafter, experiments performed to verify the effects of theelectrode assembly of the present disclosure will be described.

COMPARATIVE EXAMPLE

In an electrode assembly in which the edge parts of separators were notoverlapped, 20 to 24% of shrinkage ratio was found after heating at 150°C. for 30 minutes.

Experimental Example 1

In an electrode assembly in which the edge parts of separators wereoverlapped but not attached, and a sealing part A was not formed, 16 to18% of shrinkage ratio was found after heating at 150° C. for 30minutes.

Experimental Example 2

In an electrode assembly in which the edge parts of separators wereattached, and a sealing part A was formed, 9 to 12% of shrinkage ratiowas found after heating at 150° C. for 30 minutes.

When comparing the shrinkage ratio of Experimental Example 1 with thatof Comparative Example, the shrinkage ratio of the separator was foundto decrease when the edge parts of the separator were overlapped whencompared to that of the separator when the edge parts of the separatorswere not overlapped and separately stacked between the cathodes and theanodes.

In addition, when comparing the shrinkage ratio of Experimental Example2 with that of Experimental Example 1, the shrinkage ratio of theseparator was found to decrease when the edge parts of the separatorswere overlapped and attached to form a sealing state when compared tothat of the separators simply and doubly overlapped at the edge parts ofthe separators.

In the electrode assembly according to the present disclosure, thedecreasing effect of the shrinkage ratio due to the overlapping and thedecreasing effect of the shrinkage ratio due to the attachment of theseparators are combined, and the shrinkage ratio of the separators maybe markedly decreased.

Accordingly, the possibility of generating short between the cathode andthe anode is very low, and the stability of the electrode assembly isimproved in the present disclosure when compared to a common technology.In addition, an electrode assembly having improved stability whenconsidering the common electrode assembly may be manufactured eventhough a separator having the same size or somewhat smaller size thanthe common technology is used.

Since the area of the separator necessary for the manufacture of anelectrode assembly having the stability similar to that of the commontechnology is smaller than the common technology, the volume of asecondary battery may decrease.

In addition, since a separator having a smaller area when consideringthe common technology is used, the production cost of an electrodeassembly may decrease.

While the present invention has been shown and described in connectionwith the exemplary embodiments, it will be apparent to those skilled inthe art that modifications and variations can be made without departingfrom the spirit and scope of the invention as defined by the appendedclaims.

DESCRIPTION OF REFERENCE NUMERALS

-   100 a-100 n: cell stack parts-   110 a-110 e: radical units-   111: first electrode-   112: first separator-   113: second electrode-   114: second separator-   116: terminal electrode-   117: terminal separator-   121: first electrode material-   122: first separator material-   123; second electrode material-   124: second separator material-   130 a-130 f: first auxiliary units-   140 a-140 f: second auxiliary units-   A: sealing part

What is claimed is:
 1. An electrode assembly, comprising: a cell stackpart having (a) a structure in which one kind of radical unit isrepeatedly disposed, the one kind of radical unit having same number ofelectrodes and separators which are alternately disposed and integrallycombined, or (b) a structure in which at least two kinds of radicalunits are disposed in a predetermined order, the at least two kinds ofradical units each having same number of electrodes and separators whichare alternately disposed and integrally combined; wherein the one kindof radical unit of (a) has a four-layered structure in which a firstelectrode, a first separator, a second electrode and a second separatorare sequentially stacked together or a repeating structure in which thefour-layered structure is repeatedly stacked; wherein each of the atleast two kinds of radical units of (b) are stacked by ones in thepredetermined order to form the four-layered structure or the repeatingstructure in which the four-layered structure is repeatedly stacked,wherein the separator has a larger size than the electrode to expose anedge part of the separator to the outside of the electrode and theseparator; wherein the edge parts of the separators included in oneradical unit are attached to each other to form a sealing part, or theedge parts of the separators included in the cell stack part areattached to each other to form the sealing part, and wherein adhesivestrength between the electrode and the adjacent separator in the radicalunit is greater than adhesive strength between the radical units in thecell stack part.
 2. The electrode assembly of claim 1, furthercomprising a separator additionally stacked on an uppermost or lowermostelectrode of the cell stack part.
 3. The electrode assembly of claim 1,wherein the sealing part is formed by placing the edge parts of adjacentseparators to meet each other and by applying heat and pressure.
 4. Theelectrode assembly of claim 3, wherein an applying time of the heat andthe pressure to the edge parts of the adjacent separators to form thesealing part is 3 to 5 seconds.
 5. The electrode assembly of claim 3,wherein the pressure applied to the edge parts of the adjacentseparators to form the sealing part is smaller than a pressure appliedto attach the electrode to the separator in each of the radical units.6. The electrode assembly of claim 1, wherein the one kind of radicalunit of (a) comprises a first radical unit having the four-layeredstructure or the repeating structure in which the four-layered structureis repeatedly stacked, and wherein the cell stack part has a structurein which the first radical units are repeatedly disposed.
 7. Theelectrode assembly of claim 1, wherein the at least two kinds of radicalunits of (b) comprises: a second radical unit having the firstelectrode, the first separator, the second electrode, the secondseparator, the first electrode, and the first separator, which aresequentially disposed and integrally combined; and a third radical unithaving the second electrode, the second separator, the first electrode,the first separator, the second electrode, and the second separator,which are sequentially disposed and integrally combined, and wherein thecell stack part has a structure in which the second radical unit and thethird radical unit are alternately disposed.
 8. The electrode assemblyof claim 1, wherein the one kind of radical unit is provided inplurality and the plurality of one kind of radical units is classifiedinto at least two groups having different sizes, and wherein the cellstack part has a structure in which a plurality of steps is formed bystacking the one kind of radical units of (a) according to the sizethereof.
 9. The electrode assembly of claim 1, wherein the one kind ofradical unit of (a) is provided in plurality and the plurality of theone kind of radical units is classified into at least two groups havingdifferent geometric shapes, and wherein the cell stack part has astructure in which a plurality of steps is formed by stacking the onekind of radical units of (a) according to the geometric shape thereof.10. The electrode assembly of claim 1, wherein the electrode is attachedto an adjacent separator in each radical unit.
 11. The electrodeassembly of claim 10, wherein an entire surface of the electrode facingthe adjacent separator is attached to the adjacent separator.
 12. Theelectrode assembly of claim 10, wherein the attachment between theelectrode and the separator is provided by applying pressure to theelectrode and the adjacent separator or by applying pressure and heat tothe electrode and the adjacent separator.
 13. The electrode assembly ofclaim 10, wherein the separator comprises a porous separator basematerial and a porous coating layer that is applied to an entire surfaceof one side or both sides of the separator base material, wherein theporous coating layer comprises a mixture of inorganic particles and abinder polymer, wherein the binder polymer binds and fixes the inorganicparticles to each other, and wherein the electrode is attached to theadjacent separator by the coating layer.
 14. The electrode assembly ofclaim 13, wherein the inorganic particles of the porous coating layerhave a densely packed structure to form interstitial volumes between theinorganic particles over the overall coating layer, and wherein a porestructure is formed in the coating layer by the interstitial volumesthat are defined by the inorganic particles.
 15. The electrode assemblyof claim 1, wherein the cell stack part further comprises a firstauxiliary unit stacked on a terminal electrode that is an uppermost or alowermost electrode, wherein, when the terminal electrode is a cathode,the first auxiliary unit is formed by stacking from the terminalelectrode, a separator, an anode, a separator, and a cathode insequence, and wherein, when the terminal electrode is an anode, thefirst auxiliary unit is formed by stacking from the terminal electrode,a separator and a cathode in sequence.
 16. The electrode assembly ofclaim 15, wherein the cathode of the first auxiliary unit comprises: acurrent collector; and an active material coated on only one side facingthe radical unit among both sides of the current collector.
 17. Theelectrode assembly of claim 1, wherein the cell stack part furthercomprises a second auxiliary unit on a terminal separator that is anuppermost or a lowermost separator, wherein, when the electrodecontacting the terminal separator is a cathode in the radical unit, thesecond auxiliary unit is formed by stacking from the terminal separator,an anode, a separator and a cathode in sequence, and wherein, when theelectrode contacting the terminal separator is an anode in the radicalunit, the second auxiliary unit is formed as a cathode.
 18. Theelectrode assembly of claim 17, wherein the cathode of the secondauxiliary unit comprises: a current collector; and an active materialcoated on only one side facing the radical unit among both sides of thecurrent collector.
 19. The electrode assembly of claim 1, wherein thecell stack part further comprises a first auxiliary unit stacked on aterminal electrode disposed on an uppermost or a lowermost electrode,wherein, when the terminal electrode is a cathode, the first auxiliaryunit is formed by stacking from the terminal electrode, a separator andan anode in sequence, and wherein, when the terminal electrode is ananode, the first auxiliary unit is formed by stacking from the terminalelectrode, a separator, a cathode, a separator and an anode in sequence.20. The electrode assembly of claim 19, wherein the first auxiliary unitfurther comprises a separator at an outer side of the anode.
 21. Theelectrode assembly of claim 1, wherein the cell stack part furthercomprises a second auxiliary unit on a terminal separator that is anuppermost or a lowermost separator, wherein, when the electrodecontacting the terminal separator is a cathode in the radical unit, thesecond auxiliary unit is formed as an anode, and wherein, when theelectrode contacting the terminal separator is an anode in the radicalunit, the second auxiliary unit is formed by stacking from the terminalseparator, a cathode, a separator, and an anode in sequence.
 22. Theelectrode assembly of claim 21, wherein the second auxiliary unitfurther comprises a separator at an outer side of the anode.
 23. Theelectrode assembly of claim 1, wherein the cell stack part furthercomprises a second auxiliary unit stacked on a terminal separator thatis an uppermost or a lowermost separator, and wherein, when theelectrode contacting the terminal separator in the radical unit is ananode, the second auxiliary unit is formed by stacking from the terminalseparator, a first cathode, a separator, an anode, a separator, and asecond cathode in sequence.
 24. The electrode assembly of claim 23,wherein the second cathode of the second auxiliary unit comprises: acurrent collector; and an active material coated on only one side facingthe radical unit among both sides of the current collector.
 25. Theelectrode assembly of claim 1, wherein the cell stack part furthercomprises a second auxiliary unit stacked on a terminal separator thatis an uppermost or a lowermost separator, and wherein, when theelectrode contacting the terminal separator is a cathode in the radicalunit, the second auxiliary unit is formed by stacking from the terminalseparator, a first anode, a separator, a cathode, a separator, and asecond anode in sequence.
 26. A method of manufacturing an electrodeassembly, the method comprising: a step of forming one kind of a radicalunit having an alternately stacked structure of a same number ofelectrodes and separators, or at least two kinds of radical units havingan alternately stacked structure of a same number of electrodes andseparators (S10); a step of forming a sealing part by facing edge partsof the separators included in one radical unit and applying heat andpressure (S20); and a step of forming a cell stack part by repeatedlystacking the one kind of the radical units after performing Steps S10and S20, or by stacking the at least two kinds of the radical unitsafter performing Steps S10 and S20 in a predetermined order (S22);wherein the one kind of radical unit has a four-layered structure inwhich a first electrode, a first separator, a second electrode and asecond separator are sequentially stacked together or a repeatingstructure in which the four-layered structure is repeatedly stacked;wherein each of the at least two kinds of radical units are stacked byones in the predetermined order to form the four-layered structure orthe repeating structure in which the four-layered structure isrepeatedly stacked, and wherein adhesive strength between the electrodeand the adjacent separator in the radical unit is greater than adhesivestrength between the radical units in the cell stack part.
 27. A methodof manufacturing an electrode assembly, the method comprising: a step offorming one kind of a radical unit having an alternately stackedstructure of a same number of electrodes and separators, or at least twokinds of radical units having an alternately stacked structure of a samenumber of electrodes and separators (S10); a step of forming a cellstack part by repeatedly stacking the one kind of the radical units, orby stacking the at least two kinds of the radical units in apredetermined order (S14); and a step of forming a sealing part byfacing edge parts of the separators included in the cell stack part andapplying heat and pressure (S30); wherein the one kind of radical unithas a four-layered structure in which a first electrode, a firstseparator, a second electrode and a second separator are sequentiallystacked together or a repeating structure in which the four-layeredstructure is repeatedly stacked; wherein each of the at least two kindsof radical units are stacked by ones in the predetermined order to formthe four-layered structure or the repeating structure in which thefour-layered structure is repeatedly stacked, and wherein adhesivestrength between the electrode and the adjacent separator in the radicalunit is greater than adhesive strength between the radical units in thecell stack part.
 28. The method of manufacturing an electrode assemblyof claim 26, wherein Step S20 is performed by applying the heat of 50°C. to 100° C. and the pressure of 10 gf/cm2 to 20 gf/cm2 to the edgeparts of the separators.
 29. The method of manufacturing an electrodeassembly of claim 26, wherein an applying time of the heat and thepressure to the edge parts of the adjacent separators to form thesealing part is 3 to 5 seconds.
 30. The method of manufacturing anelectrode assembly of claim 26, wherein the pressure applied to the edgeparts of the adjacent separators is smaller than a pressure applied toattach the electrode to the separator.